Pflügers Archiv

, Volume 392, Issue 2, pp 163–167 | Cite as

Effects of CO2, acetylcholine and caerulein on45Ca efflux from isolated mouse pancreatic fragments

  • O. H. Petersen
  • R. C. Collins
  • I. Findlay
Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands

Abstract

Mouse pancreatic fragments were loaded with45Ca and placed in a flow cell. The concentration of45Ca in the effluent was measured. The effects of changing the tension of carbon dioxide on45Ca efflux were observed and compared with effects of pancreatic secretagogues.

The normal control solution was equilibrated with 5% CO2, 95% O2. Shift to solutions equilibrated with 10, 20, 50 or 100% CO2 evoked a dose-dependent increase in fractional45Ca efflux, with a just detectable effect at 10% and a maximal one at 50%.

The CO2-evoked Ca release was not due to anoxia, since a short period of exposure to a 100% N2-equilibrated solution had no effect. A decrease in extracellular pH (tris buffering) had only a very modest effect on45Ca efflux.

CO2-evoked Ca release under conditions avoiding extracellular pH changes (20% CO2, 100 mM NaHCO3). This CO2-evoked enhanced45Ca efflux was sustained during a 30 min stimulation period, but was abruptly terminated on return to the control solution (5% CO2, 25 mM NaHCO3). NH3 (10 mM) added to the 20% CO2-equilibrated solution for a brief interval in the middle of a period of CO2-evoked enhanced45Ca efflux evoked a rapid return of the fractional Ca efflux towards the resting level. This effect was rapidly reversible.

While the CO2-evoked Ca release was largely sustained, the ACh-evoked increase in45Ca fractional efflux was entirely transient. The CO2-evoked Ca release was not inhibited by a background of sustained ACh stimulation. ACh-evoked Ca release, however, was markedly inhibited in the presence of sustained CO2 stimulation.

2,4 Dinitrophenol (1 mM) in combination with iodoacetate (2 mM), while markedly reducing45Ca uptake into the fragments during the loading period had little or no effect on the ACh-evoked increase in45Ca fractional efflux. The CO2-evoked Ca release, however, was markedly reduced by these metabolic inhibitors.

The local anaesthetic procaine (1 mM) virtually abolished ACh- or caerulein-evoked Ca release without having any influence on the CO2 effect.

It is concluded that CO2 releases Ca from pancreatic acinar cells by means of intracellular acidification. This effect may in part be due to H+ displacement of Ca2+ from intracellular membrane binding sites and partly due to release of Ca from compartments (organelles) into which Ca has been actively accumulated.

Key words

Pancreas Acinar cell CO2 Intracellular acidification Ca transport Ca2+−H+ interaction ACh Caerulein 

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References

  1. Boron WF, De Weer P (1976) Intracellular pH transients in squid giant axons caused by CO2, NH3 and metabolic inhibitors. J Gen Physiol 67:91–112Google Scholar
  2. Caldwell PC (1958) Studies on the internal pH of large muscles and nerve fibres. J Physiol (Lond) 142:22–62Google Scholar
  3. Case RM, Clausen T (1973) The relationship between calcium exchange and enzyme secretion in the isolated rat pancreas. J Physiol (Lond) 235:75–102Google Scholar
  4. Deschodt-Lanckman M, Robberecht P, De Neef P, Lammens M, Christophe J (1976) In vitro action of bombesin and bombesin-like peptides on amylase secretion, calcium efflux, and adenylate cyclase activity in the rat pancreas. A comparison with other secretagogues. J Clin Invest 56:366–375Google Scholar
  5. Gardner JD (1979) Regulation of pancreatic exocrine function in vitro. Initial steps in the action of secretagogues. Ann Rev Physiol 41:55–66Google Scholar
  6. Gardner JD, Jensen RT (1981) Regulation of pancreatic enzyme secretion in vitro. In: Johnson LR (ed) Physiology of the gastrointestinal tract. Ch 32. Raven Press, New York, pp 831–871Google Scholar
  7. Gardner JD, Conlon TP, Klaeveman HL, Adams TD, Ondetti MA (1975) Action of cholecystokinin and cholinergic agents on calcium transport in isolated pancreatic acinar cells. J Clin Invest 56:366–375Google Scholar
  8. Hertzberg EL, Lawrence TS, Gilula NB (1981) Gap junctional communication. Ann Rev Physiol 43:479–491Google Scholar
  9. Iwatsuki N, Petersen OH (1977) Acetylcholine-like effects of intracellular calcium application in pancreatic acinar cells. Nature 268:147–149Google Scholar
  10. Iwatsuki N, Petersen OH (1978a) Pancreatic acinar cells: acetylcholineevoked electrical uncoupling and its ionic dependency. J Physiol (Lond) 274:81–96Google Scholar
  11. Iwatsuki N, Petersen OH (1978b) Electrical coupling and uncoupling of exocrine acinar cells. J Cell Biol 79:533–545Google Scholar
  12. Iwatsuki N, Petersen OH (1978c) Effect of carbon dioxide on electrical communication between pancreatic acinar cells. J Physiol (Lond) 284:48–49PGoogle Scholar
  13. Iwatsuki N, Petersen OH (1979) Pancreatic acinar cells: the effect of carbon dioxide, ammonium chloride and acetylcholine on intercellular communication. J Physiol (Lond) 291:317–326Google Scholar
  14. Kondo S, Schulz I (1976a) Calcium ion uptake in isolated pancreas cells induced by secretagogues. Biochim Biophys Acta 419:76–92Google Scholar
  15. Kondo S, Schulz I (1976b) Ca2+ fluxes in isolated cells of rat pancreas. Effect of secretagogues and different Ca2+ concentrations. J Membr Biol 29:185–203Google Scholar
  16. Lea TJ, Ashley CC (1978) Increase in free Ca2+ in muscle after exposure to CO2. Nature 275:236–238Google Scholar
  17. Laugier R, Petersen OH (1980) Pancreatic acinar cells: electrophysiological evidence for stimulant-evoked increase in membrane calcium permeability in the mouse. J Physiol (Lond) 303:61–72Google Scholar
  18. Matthews EK, Petersen OH, Williams JA (1973) Pancreatic acinar cells: acetylcholine-induced membrane depolarization, calcium efflux and amylase release. J Physiol (Lond) 234:689–701Google Scholar
  19. Petersen OH, Iwatsuki N (1978) The role of calcium in pancreatic acinar cell stimulus-secretion coupling: an electrophysiological approach. Ann NY Acad Sci 307:599–617Google Scholar
  20. Petersen OH, Ueda N (1976) Pancreatic acinar cells: the role of calcium in stimulus-secretion coupling. J Physiol (Lond) 254:583–606Google Scholar
  21. Petersen OH, Findlay I, Daoud M, Collins RC (1981) Functional organization of cells in exocrine gland acini. In: Pitts JD (ed) Functional integration of cells in animal tissue. Cambridge University Press (in press)Google Scholar
  22. Rose B, Rick R (1978) Intracellular pH, intracellular free Ca and junctional cell-cell coupling. J Membr Biol 44:377–415Google Scholar
  23. Rink TJ, Tsien RW, Warner AE (1980) Free calcium in Xenopus embryos measured with ion-selective microelectrodes. Nature 283:658–660Google Scholar
  24. Schreurs VVAM, Swarts HGP, De Pont JJHHM, Bonting SL (1975) Role of calcium in exocrine pancreatic secretion. I. Calcium movements in the rabbit pancreas. Biochim Biophys Acta 404:257–267Google Scholar
  25. Schulz I (1980) Messenger role of calcium in function of pancreatic acinar cells. Am J Physiol 239:G335–347Google Scholar
  26. Schulz I, Stolze HH (1980) The exocrine pancreas: the role of secretagogues, cyclic nucleotides, and calcium in enzyme secretion. Ann Rev Physiol 42:127–156Google Scholar
  27. Stolze HH, Schulz I (1980) Effect of atropine, ouabain, antimycin A, and A23187 on the “trigger Ca2+ pool” in exocrine pancreas. Am J Physiol 238:G338–348Google Scholar
  28. Thomas RC (1974) Intracellular pH of snail neurones measured with a new pH-sensitive glass microelectrode. J Physiol (Lond) 238:159–180Google Scholar
  29. Turin L, Warner AE (1980) Intracellular pH in early Xenopus embryos: its effect on current flow between blastomeres. J Physiol (Lond) 300:489–504Google Scholar

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • O. H. Petersen
    • 1
  • R. C. Collins
    • 1
  • I. Findlay
    • 1
  1. 1.Department of PhysiologyThe UniversityDundeeUK

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